Re: from __future__ import absolute_import ?

Ron Adam wrote:

Peter Otten wrote:
Ron Adam wrote:

from __future__ import absolute_import

Is there a way to check if this is working? I get the same results with
or without it.

Python 2.5 (r25:51908, Sep 19 2006, 09:52:17)
[MSC v.1310 32 bit (Intel)] on win 32

If there are two modules 'foo', one at the toplevel and the other inside
a package 'bar',

from __future__ import absolute_import
import foo

will import the toplevel module whereas

import foo

will import bar.foo. A messy demonstration:

$ ls bar
absolute.py foo.py __init__.py relative.py
$ cat bar/absolute.py
from __future__ import absolute_import
import foo
$ cat bar/relative.py
import foo
$ cat foo.py
print "toplevel"
$ cat bar/foo.py
print "in bar"
$ python2.5 -c 'import bar.absolute'
toplevel
$ python2.5 -c 'import bar.relative'
in bar


Another example is here:

http://mail.python.org/pipermail/python-list/2007-January/422889.html

Peter

Thanks, that helped, I see why I was having trouble.


work
|
|- foo.py # print "foo not in bar"
|
`- bar
|
|- __init__.py
|
|- foo.py # print "foo in bar"
|
|- absolute.py # from __futer__ import absolute_import
| # import foo
|
`- relative.py # import foo


* Where "work" is in the path.


(1)

C:\work>python -c "import bar.absolute"
foo not in bar

C:\work>python -c "import bar.relative"
foo in bar


(2)

C:\work>python -m "bar.absolute"
foo not in bar

C:\work>python -m "bar.relative"
foo not in bar


(3)

C:\work>python
Python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit (Intel)]
on win 32
Type "help", "copyright", "credits" or "license" for more information.
>>> import bar.absolute
foo not in bar
>>> import bar.relative
foo in bar


(4)

C:\work>cd bar

A path below the package level is generally a good means to shoot yourself
in the foot and should be avoided with or without absolute import.

C:\work\bar>python -c "import bar.absolute"
foo in bar

C:\work\bar>python -c "import bar.relative"
foo in bar


(5)

C:\work\bar>python
Python 2.5 (r25:51908, Sep 19 2006, 09:52:17) [MSC v.1310 32 bit (Intel)]
on win 32
Type "help", "copyright", "credits" or "license" for more information.
>>> import bar.absolute
foo in bar
>>> import bar.relative
foo in bar
>>>



Case (2) seems like it is a bug.

I think so, too.

Why not also have (4), and (5) do the same as cases (1) and (3)?

The work/bar directory is the current working directory and occurs in the
path before the work directory. When bar.absolute imports foo python is
unaware that work/bar/foo.py is part of the bar package.

in cases (4) and (5), that is the result I would expect if I did:

import absolute # with no 'bar.' prefix.
import relative


From what I understand, in 2.6 relative imports will be depreciated, and
in 2.7
they will raise an error. (providing plans don't change)

Would that mean the absolute imports in (4) and (5) would either find the
'foo not in bar' or raise an error?

No, in 1, 3 -- and 2 if the current behaviour is indeed a bug. This is only
for the relative import which would have to be spelt

from . import foo

in an absolute-import-as-default environment;

import foo

would always be an absolute import.

If so, is there any way to force (warning/error) behavior now?

I don't know.

Peter

.

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